Do you have trouble finding your keys? Can't remember names and faces?

The BBC News reports on a study to be presented to the American Academy of Neurology that concludes that people who keep themselves mentally active between the ages of 50 and 65 have a better chance of delaying the onset of dementia than people who watch television.

And where does playing video games fit into this, I wonder? Does it count as watching TV, or remaining mentally active? My father is something of an avid gamer, so it has something of a personal relevance.